1. Scope of Invention
This invention relates generally to hypodermic syringes and particularly to an improvement in the hypodermic syringe handle for sensing manual thumb force proportional to medication injection flow rate and pressure.
2. Prior Art
An operator in making an injection determines the rate of speed of medication injection. It is known that the faster a fluid is injected into tissue, the more painful it can be for the recipient of the injection. Inadvertent hasty injections are commonplace. If there were a consistent way to determine the flow rate and pressure applied to the fluid in the ampule which is being injected out the needle tip, it would be possible to sense the amount of pressure that should be applied to the plunger, thus allowing the operator to push fluid from the ampule at a flow rate and pressure just shy of the threshold at which pain is sensed.
In the medical, dental and veterinary fields, cartridge ampules of injectable fluid are now commonly used in hypodermic syringes. Such ampules usually comprise a cylindrical container of glass or clear plastic material, the forward end of which is sealed by a rubber membrane and the rear end of which is sealed by a rubber piston which is slidable within the container. In use, such cartridge ampules are positioned within the barrel of a syringe so that the membrane is pierced by the rear end of a needle and the rubber piston is advanced into the container by manual thumb force against a thumb-operated plunger to inject the fluid through the needle into the patient.
It is commonly known among those who administer medicines or anesthetics subcutaneously or intramuscularly, that pain can be elicited due to a number of factors such as the number of pain receptors at the injection site, fluid temperature, the liquid agent being administered, and the speed or flow rate and pressure at which the agent is being administered.
Little can be done to control the site-specific area where the medicine is to be administered. The use of topical agents can help reduce the pain from the needle puncture wound, but this is not always successful. The medicine can sometimes be warmed to body temperature, thus reducing the pain elicited from the dissimilar temperature between the medicine and site. This too does not always work, since many medicines cause pain simply by being administered. It is a well-known fact that administering the medicine more slowly can often ease the amount of pain that is elicited at the site, in particular with injectable anesthetics.
The difficulty many operators have while administering injectable medicines is the lack of tactile sensitivity relating to how hard or how much pressure should be applied to push the syringe plunger to express the medicine, especially when there is an apprehensive patient or when the practitioner loses tactile feel because of the use of gloves for barrier protection.
One solution to this problem provided by the present invention is to create a device whereby the individual administering the injectable medicine consistently senses an indicator of the amount of applied injection pressure and, thusly, medication flow rate. After the needle has been inserted into the area to be injected in a conventional manner, the syringe plunger thumb ring or plate is depressed to create the necessary pressure to express the medicine from the ampule into the tissue or site. The invention allows the operator to apply a consistent reproducible pressure at a threshold just shy of that at which pain can be sensed. As a result, injections are more consistent and smooth, resulting in a comfortable injection for the patient. At the same time, this consistency builds operator confidence which yields decreased stress for the operator while performing the injection.